Heretofore, aluminum (Al) or Al alloy has widely been used as a conductive material in silicon semiconductor integrated circuits (LSI). As manufacturing methods of LSIs make progress in fineness, copper (Cu) has increasingly been used as a conductive material to reduce the wiring resistance of interconnections and to enhance the reliability of interconnections. Cu readily diffuses into a silicon oxide film. Accordingly, a conductive barrier metal film for preventing Cu from diffusing is used on side surfaces and lower surfaces of Cu interconnections, and an insulating barrier film is used on upper surfaces of Cu interconnections.
The recent development of the fineness in LSIs has further reduced the interconnection dimension, so that an increase of the capacity between interconnections has been problematic. Therefore, porous low-dielectric-constant films have increasingly been introduced to interlayer dielectrics for the following reason. Because high-speed and low-power connection is required in a case where multilayer interconnections are used in a semiconductor device, reduction of the dielectric constant of interlayer dielectrics is effective in addition to the improvement of the fineness. It has been desired to meet both of these demands.
In order to reduce an effective capacity between interconnections, reduction of the dielectric constant of interlayer dielectrics (to a dielectric constant lower than that of a silicon oxide film (k=4.2)) has been required. Examples of low-dielectric-constant films include an HSQ (Hydrogen Silsesquioxane) film, a CDO (Carbon doped oxide) or organic film, and the like. Those low-dielectric-constant films are formed by a spin-coating method, a vapor phase method, or the like.
Japanese laid-open patent publication No. 2004-289105 (Patent Document 1) discloses a technique of forming a porous insulating film by using a plasma CVD method. Published Japanese patent translation No. 2002-526916 (Patent Document 2) discloses a technique of forming a porous insulating film by using cyclic organosiloxane. Japanese laid-open patent publication No. 2004-200713 (Patent Document 3) discloses a technique of changing the total pressure of a reaction chamber so as to improve the adhesion of an insulating film.